云南八宝石炭─二叠系界线地层的古地磁研究

滇东南八宝安乐剖面，是石炭—二叠系界线地层的典型剖面．根据古生物演化、地史特征，把界线置于八宝阶的底，或Ｐｓｅｕｄｏｓｃｈｗａｇｅｒｕｉｎａｕｄｄｅｎｉ带或Ｓｔｒｅｐｔｏｇｎａｔｈｏｄｕｓｅｌｏｎｇａｔｕｓ带之底．这一生物界线完全可与北美、日本、大洋洲、欧洲的界线相对比，它与世界上许多重要国家的界线一致，因此，它具有全球的科学意义．古地磁结果表明，八宝剖面受现代地磁场的影响较小，３２个样品中的５个样品为Ａ组方向，是现代地磁场重磁化的产物，多数为Ｂ组方向，是古代地磁场的磁化方向，可以确定为反向板化；只有４号样为Ｃ组方向，也是天然剩磁方向，为正向极化．八宝剖面主要为反极性段地层，并夹有一个短暂的正极性带，以第３层底部具有极性倒转的Ｂ点作为石炭─二叠系的界线点是可行的，更进一步证实该生物界线的正确性，科学性地极的转向，在全球是等时的，在长期反向的基亚曼极性段中，短暂的正向极性间隔带，是确定界线的确切空间．

Further Study on Palaeomagnetism of the Carboniferous -Permain Boundary Stratigraphy at Babao,Yunnan

The babao section in South-eastern of Yunnan is one of standard section of the Carboniferous-Permain Boundary Stratiphy.According to the features of Paleontological evolution and geohistory development the boundary is put at the bottom of the Bobao Stage or Pseudoschwagerina udden zone or Streptognathodus elogatus zone.The biological boundary is similar to those in many other countries in the world. Thus,it should have a great scientific value on the globe.A total of 32 samples were collected from the sequence of carbonate rocks at this section.The results of thermal demagnetization indicate that there are three groups of magnetic derections.They are A,B and C groups. Group A has been strongly overprinted by the recent strong magnetic field while group B and group C still have preserved stable remanent magnetism that poins to the north or south with antipodal directions. A great majority of rocks at the section belongs to group B,possessing a antipolarity,but only sample No.4 belongs to group C, possessing orthopolarity.In conclusion,we can say,that is high correlation between palaeomagnetic and the bidogic boundary,point B reversed on the bottom of layer 3 at the section is the boundary point of carboniferous and Permain.A short orthopolarity zonation in a long Guiyama antipolaritical stage is also to define vertical distributional range of the boundary.